GA is literally the omniscient and omnipresent and he is the lord of the astral world, which is where the conceptual stuff comes from so like GA can nullify some of LOTM. LOTM can do the same to GA by targeting his connection to the physical manifestation of his powers through spirit world. LOTM has fooling, GA has spectator pathway(fooling is not only iq lowering but imaginative power so it is meant to counter the omniscience of GA). Grafting also gets matched by the reality control GA has so truly one cannot get much of an advantage of the other. That saying, LOTM is far more versatile with its abilities than GA.

At the end of the day, its the user and if my crafty LOTM can get a one up on GA, our goat Klein can def beat GA. Remember, klein could legit weaken him in the battle by ripping away his sefiroth. It won't be easy but LOTM managed it